1. Field
The disclosure relates to a method, system, and article of manufacture for the communication of conditions at a primary storage controller to a host.
2. Background
A host may be coupled to a primary storage controller and a secondary storage controller. Storage volumes in the primary storage controller may be copied via synchronous peer to peer remote copy operations to the secondary storage controller. The primary and secondary storage controllers may in such a situation be referred to as being in a mirrored configuration.
The host may issue write requests to the primary storage controller, and the primary storage controller may replicate the writes to the secondary storage controller; the secondary storage controller may acknowledge the writes to the primary storage controller, and the primary storage controller may then acknowledge the writes to the host.
In certain situations, the host may not be able to perform I/O operations with one or more storage volumes of the primary storage controller. The inability to perform I/O operations with one or more storage volumes of the primary storage controller may be because of the failure of the one or more storage volumes in the primary storage controller, or because of the failure of the primary storage controller itself. In such situations, the host may be able to substitute usage of the primary storage controller with the secondary storage controller (i.e., use the secondary storage controller instead of primary storage controller), such that host applications may continue to execute.
If a host application was previously accessing the primary storage controller and received indications of I/O failures, then swapping of the primary storage controller by the secondary storage controller that maintains copies of the storage volumes of the primary storage controller allows the host application to continue execution. From the host application perspective, the swapping is transparent, i.e., host applications do not have to be aware that a swapping took place.